Classic. I hate any other way.
I'd actually like to use both. (For the forums with 10000 addons) Have the name one way addons the other. Would be much niver.
For a business type forum, I prefer Horizontal. Minimal information is displayed, and it puts more emphasis on the actual post content.
For fun/hobby sites, I go with Classic, because there is generally a lot more I like to put in the postbit, and there isn't much you can do with Horizontal in the way of additional information.